/*
 * Copyright (C) 2013, Pavel Samko <bulldozerbsg@gmail.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the "Pavel Samko" nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */

#include "vfscrypttea.h"
#include <string.h>

void vfs_tea_encrypt_block(uint32_t block[2], uint32_t key[4])
{
	size_t i;
	uint32_t sum = 0;
	uint32_t delta = 0x9e3779b9;
	for (i = 0; i < 32; ++i)
	{
		sum += delta;
		block[0] += ((block[1] << 4) + key[0]) ^ (block[1] + sum) ^ ((block[1] >> 5) + key[1]);
		block[1] += ((block[0] << 4) + key[2]) ^ (block[0] + sum) ^ ((block[0] >> 5) + key[3]);
	}
}

void vfs_tea_decrypt_block(uint32_t block[2], uint32_t key[4])
{
	size_t i;
	uint32_t sum = 0xc6ef3720;
	uint32_t delta = 0x9e3779b9;
	for (i = 0; i < 32; ++i)
	{
		block[1] -= ((block[0] << 4) + key[2]) ^ (block[0] + sum) ^ ((block[0] >> 5) + key[3]);
		block[0] -= ((block[1] << 4) + key[0]) ^ (block[1] + sum) ^ ((block[1] >> 5) + key[1]);
		sum -= delta;
	}
}

void vfs_tea_encrypt(void * data, size_t data_size, uint32_t key[4])
{
	uint8_t * p = (uint8_t *)data;
	data_size = data_size / VFS_TEA_BLOCKSIZE * VFS_TEA_BLOCKSIZE;
	if (p)
	{
		while (data_size)
		{
			vfs_tea_encrypt_block((uint32_t *)p, key);
			data_size -= VFS_TEA_BLOCKSIZE;
			p += VFS_TEA_BLOCKSIZE;
		}
	}
}

void vfs_tea_decrypt(void * data, size_t data_size, uint32_t key[4])
{
	uint8_t * p = (uint8_t *)data;
	data_size = data_size / VFS_TEA_BLOCKSIZE * VFS_TEA_BLOCKSIZE;
	if (p)
	{
		while (data_size)
		{
			vfs_tea_decrypt_block((uint32_t *)p, key);
			data_size -= VFS_TEA_BLOCKSIZE;
			p += VFS_TEA_BLOCKSIZE;
		}
	}
}
